Conventionally, powder supplying devices for accommodating a mass toner, such as toner banks and toner replenishing devices, are known for use in image forming devices, such as copiers or printers. For example, see Japanese Patent No. 3534159 and Japanese Laid-Open Patent Application No. 2005-024622.
Japanese Patent No. 3534159 discloses a powder supplying device (toner bank) in which a plurality of toner containers in the shape of toner bottles are installed. Specifically, one of the plurality of toner containers is opened, and the toner contained in the toner container is supplied to a toner hopper of the toner bank. The toner in the toner hopper is transported by a gas-flow transporting unit to a developing device which is a powder receiving device. And when the toner in the opened toner container becomes empty, another toner container among the plurality of toner containers is opened and toner replenishment is performed with the newly opened toner container.
Japanese Laid-Open Patent Application No. 2005-024622 discloses a toner replenishing device in which a toner hopper having a capacity larger than the capacity of a toner container is provided. Specifically, the toner hopper is capable of containing an amount of toner equivalent to the amount of toner contained in the plurality of toner containers. A stirring member is installed in the toner hopper and the toner inside the toner hopper is agitated by the stirring member. And the toner in the toner hopper is discharged from the lower part of the toner hopper, and is transported by a fluid transporting unit to a developing device which is a powder receiving device.
Moreover, Japanese Patent No. 3549051 discloses a powder supplying device (powder filling apparatus) which is adapted for filling up a toner container (powder container) with toner (powder). Specifically, air is introduced into the powder filling apparatus, and the air pressure in the powder filling apparatus is increased, so that the toner (powder) contained in the powder filling apparatus is discharged from a powder transport tube, and it is transported to a toner container which is a powder receiving device.
Since a plurality of toner containers are installed in the powder supplying device of Japanese Patent No. 3534159, transporting of a large amount of toner is attained. However, after all the toner contained in the plurality of toner containers becomes empty, the setting work of a number of new toner containers corresponding to the number of the used toner containers will arise. Therefore, there is the problem that the workability at the time of toner end does not improve even if transporting of a large amount of toner is attained.
The powder supplying device of Japanese Laid-Open Patent Application No. 2005-024622 uses a large-capacity toner hopper which is aimed at transporting of a large amount of toner. However, since the toner in the toner hopper is mechanically agitated by the stirring member in order to prevent bridge formation of the toner contained in the hopper, mechanical stress may arise in the toner. If mechanical stress arises in the toner, the additive agent included in the toner may be deviated in the toner surface or separated from the toner surface. Even if the toner is a new toner, the toner is in a deteriorated condition, which will cause the quality of image to be lowered.
Moreover, the powder supplying device of Japanese Laid-Open Patent Application No. 2005-024622 is provided so that toner is discharged from the lower part of the toner hopper. When the sealing performance near the exhaust opening falls, the amount of toner which scatters from the powder supplying device will be increased.
The powder supplying device of Japanese Patent No. 3549051 is provided such that high pressure is applied to the container containing toner, so that the toner is discharged from the inside of the container. For this reason, it is necessary that the mechanical strength of the container is set to a sufficiently high level, so that the container may not be broken by the applied pressure.
Therefore, even if the powder supplying device of Japanese Patent No. 3549051 can be used as a manufacturing device which fills up a toner container with toner, it is difficult to use the same for supplying toner to a developing device in an image forming device. Moreover, if the method of discharging the toner from the inside of the container by applying high pressure to the container which contains toner is used, the amount of toner discharged changes sharply according to the amount of toner remaining in the container. And it is difficult to adjust finely the amount of toner discharged. Therefore, even if the powder supplying device of Japanese Patent No. 3549051 can be used as a manufacturing device which fills up a toner container with toner, it is difficult to use the same for supplying toner to a developing device in an image forming device.
The above-mentioned problems are common in all the powder supplying devices, including a powder supplying device provided in an image forming device to supply toner, which require the fine adjustment of the amount of powder supplied, without damaging the powder. And it is necessary for all those powder supplying devices to supplement powder into the powder container in appropriate timing, in order to reduce the inoperative time of the powder receiving device (or a developing device in an image forming device) when the powder contained in the powder container becomes empty.